Rocker-arm snap switch



Dad 1 2, 1950 F. c. FUKE 2,533,571

ROCKER-ARM SNAP SWITCH Filed Dec. 1, 1945 3 Sheets-Sheet 1 I M g- ,2? 5L ,2? 2a 29 I 1 66 WW w 262 J 26 M m 3? L I I 25 A H C95 Dec. 12, 1950 F. c. FUKE ROCKER-ARM SNAP SWITCH 5 SheetsSheet 2 Filed Dec. 1, 1945 Franc/5 C Fuke lnven or A (1222/ m, Wm?

Dec. 12, 1950 F. c. FUKE 2,533,571

ROCKER-ARM SNAP SWITCH Filed Dec. 1, 1945 3 Sheets-Sheet 3 rancis C4 F kQ lnvenf'or 0 117% Patented Dec. 12, 1950 UNITED STATES "ATEN T' OFF ICE Application December 1, 1945., Serial No. 632,155 In 'G'reatBritain May '30,, 1944 1 Claim.

This 'invention'rel'ates to electric 'switchesand is particularly (but not exclusively) concerned with switches of the micro-break type for the control of "alternating current.

'In "an electric switch of the tumbler type it has alreadyfbeenproposed (-see British specification No. 5'521181) to determine the length of break perpoleby a gap; which is constant, be-

tween two fixed rigid contacts, switching being effected by a. third and movable contact which in inovirrg makes rubbing and abutting contact 'with'the face "of on'e orboth of the fixed contacts under the influence "of a snap-action operating mechanism.

The present invention is concerned'with an el'ectric switch comprising in combination with two fixed contacts with a gap between them, a switch" operating member movable to and fro "between twolim-iting positions, and a movable contact element in the "from of a rocking arm,

one-end ofwhioh '(hereinafter referred to asthe 'outer'e'nd) has a floating bearing in a troughlike housing or journal provided in part by one of the 'fi-Xed contacts and in part by the other "fixed contact, and theother endo'f which '(here- "inafter referred to as the inner end) is so carried "by the "operating member that on movement-of said member between one limiting position and theother, the arm willbe rockedabout its outer end through a dead centre across the gapbe'tween'the two fixed contacts, the arrangement being such that inorre'li miting position of the operating member the outerend of the "arm abuts on both fixed contacts and. in the "otherlimiting positi'on' i-tabuts ononly one fixed contact.

"The'ro'cking arm may be spring-controlled to providea snap-actionbetween the limiting posi- According tothe' invention, the switch operating member is a slide, elg. in the form of "a In 'order-to provide a snap-action the two arms mayfbe controlled by independent springs, or'a singlecontrol' springmay be employed.

Some examples embodying the foregoing and other features of the invention will now heelesc'ribed, with reference "to the accompanying drawin'gs, which are to some extent diagram-- :maticxandin which Figure l is an elevation showing the sw itoh mechanism "according to the first example;

Figures 2 and 3 are elevations, similar to'Fi'gure 1, showing successive positions assumed by the operating parts when the switch is'mov'ed from on to off;

Figure 4 is a plan of the switch shown in Figures l to 3, the left half of the Figure being in section;

Figure 5 is a partial elevation showing a modified. arrangement of spring control; I

Figure 6 is a partial elevation showing a, modification providing a single-pole :single throw switch;

Figure 7 is an elevation of a switch mocha nism embodying a further example;

Figure 8 is a view (similar to Figure 7 showing a modification providing an intermediate control switch.

In the first example (Figures 1 to l), the switch, which is of doublapole single-throw pattern, comprises a rectangular base 253 of insu'lating material having at opposite sides .integral arcuate flanges 2! in which are formed D-shaped holes in alignment for accepting a movable operating plunger 22 of a corresponding cross-section. Mounted on the base 21) on opposite sides respectively of, and parallel to, the operating plunger 22- are two pairs of fixed contacts 23, 24. Between each pair-of the fixed contacts there is a small air gap 25. The fixed contacts 23, 2- 3 are rigidly secured to "the insulating base 29 by screws 25 and each contact i-s'prov'ide'd with a hole El and e. terminarscrew 2 8 forsecuring'the ends of the cable of the circuit to be controlled. The base 25 is provided with a pair of slightly elongated counter-bored holes 29 for accepting the screws for fastening the switch to a wall or other support. Adjacent the elongated fixing holes 29ers .threaded holes for co-operating with screws at by which a domed cover 3! is secured in position between :the base'flanges 2E after the switch has been connected 11p and secured to the wall surface. TheiCOVE! :31, 'whenin' position, completely encloses the electrical conductors and contacts within the switch base.

' 'Iheoperating-plunger'22, for convenience in assernbly, isin two parts which are secured toto gether 'interme'diate inthe length of the plunger as-a whole by a screwlEZ, in the region of which a compartment is formed within'the-plunger for accepting and housing a pairof locating pins 33, two tors-ion springs 34 associated therewith, and the inner ends of two rocking arms 35 which together constitute the movable contact member of the double-pole switch. The fixing screw 32 which connects the two plunger parts together has a plain shank extending beyond its threaded portion so as to engage with a slot 33 in the base 20. The length of the base slot 33 thus limits the movement of the operating plunger 22 in each direction. The outer end of each rocking arm 35 is of ball or roller shape and has a floating engagement with a trough-like bearing provided in the region of the air gap 25 between the two co-operating fixed contacts 23, 24 and provided in part by one fixed contact 23 and in part by the other fixed contact 24 and the tongue 24a projecting therefrom which closely approaches contact 23. Each torsion spring 34 has an eye which engages over the corresponding locating pin 33 and two arms splayed apart at an acute angle, one being a short arm 31 and the other a long arm 38. The short arms 3'! of the torsion springs are pivotally articulated to the inner ends of the rocking arms 35. The long arms 33 of the torsion springs, which are located on opposite sides respectively of the plunger fixing screw 32, bear on the opposite end walls of the intermediate plunger compartment.

The following is a description of the operation of the switch according to the first example, assuming it to be fixed to a wall surface with the operating plunger 22 disposed vertically and in its lowermost position. When the switch parts are in this position (shown in Figure 1)-which is the on position of theswitch-the reactions of the torsion springs 34 are such that the plunger 22 isforced downwardly to the limit of its travel while the rocking arms 35 are forced upwardly and outwardly into engagement with both fixed contacts 23, 24, thereby electrically connecting the switch contacts on each side of the switch. If the operating plunger 22 is now pushed upwardly against the spring reactions each rocking arm 35 will turn about an axis coincident with the centre of the ballor roller-shaped portion at the outer end of the arm, and while doing so the outer end of the arm will make effective rubbing contact against both its co-operating fixed contacts 23, 24. As the plunger 22 continues to be pushed upwardly, a position is eventually reached when each rocking arm 35 passes {a dead centre position (shown in Figure 2) with the result that the spring reactions automatically continue the upward movement of the plunger and, at the same time, force the rocking arms 35 downwardly and outwardly into positions (shown in Figure 3) in which the outer end of each arm bears only on the co-operating fixed contact 24. In this way the electrical connection between the fixed contacts on each side of the switch is broken. It will be appreciated that when movement of the plunger 22 carries the spring reactions over the dead centre position (Figure 2), the plunger automatically continues its movement and so also do the rocking arms 35 so that in either direction of movement the double-pole movable contact, constituted by the .two rocking arms, makes and breaks the circuit with a snap action.

The foregoing example, which is that of a double-pole singe-throw assembly, may readily be modified, by a simple change in the arrangement of fixed contacts and without entailing any change in the moving parts, to provide single-pole, intermediate control and other patterns of switch. Thus to provide a single-pole single-throw witch, -as illustrated in Figure 6, the fixed contacts on one side of the operating plunger 22 are omitted and a simple fixture 4| to provide a bearing for the outer end of the rocking arm 35 on that side of the operating plunger is attached to the insulating base 20.

Instead of providing separate torsion springs to control the two rocking arms, a single spring common to both arms may be employed providing the arms are electrically insulated one from the other. An arrangement of this kind is shown in Figure 5 where the levers 35 are controlled by a single compression spring 40.

In a further example (Figure 7) the outer end of each rocking arm is in the form of a rotatable roller 42 which on movement of the switch between the on and off positions makes rolling contact with the surfaces of the co-operating fixed contacts. In this example the rocking arms are controlled by U-shaped springs 43.

In Figure 8 the switch illustrated is a modified form of that shown in Figure '7, the modification being for the purpose of providing a socalled intermediate control switch. The two pairs of main fixed contacts 23, 24 are retained and in association with each pair there is furnished a third or auxiliary fixed contact 50. The location of each auxiliary fixed contact is such that in one position of the corresponding rocking arm 35 it electrically connects the auxiliary contact 50 with the fixed contact 23 and in the other position (shown in Figure 8) it electrically connects the two main fixed contacts 23, 24. The auxiliary fixed contacts 50 are cross-connected at the back of the switch with main fixed contacts on opposite sides of the operating plunger 22.

Similarly in order to furnish a single-pole double-throw switch, the following modification (as in Figure 7) may be made. On one side of the plunger 22 the fixed contacts 23, 24 are reversed in position compared with the fixed contacts on the other side of the plunger, and one fixed contact is not provided with a cable ter- ,minal hole and this fixed contact is cross-connected (preferably at the back of the switch) to Z the fixed terminal diagonally opposite. This arrangement is such that in one limiting position of the plunger 22, the outer end of the rocking arm 35 on one side of the plunger connects the corresponding pair of fixed contacts while the corresponding end of the rocking arm 35 on the other side of the plunger is in the off position.

In the above way it will be appreciated that using the same movable switch unit comprising the rocking arms, control springs and operating plunger, a variety of patterns of switch may selectively be obtained merely by incorporating, during the switch assembly process, the appropriate arrangement of fixed contacts. This is an im portant feature of the present invention which accordingly includes a method for the production in large quantities of electric switches of the single-pole, double-pole and intermediate pattern which is characterised by the manufacture of a switch movement and actuating mechanism therefor as herein described common to all of the aforesaid patterns of switch and by selective- 1y providing the particular pattern required by the association with the common movement and actuating mechanism of different fixed switch contacts appropriate respectively to the different patterns. v

I claim:

An electric snap-action switch comprising a base, two contacts fixed to the base with a gap between them, a switch operatin Plunger movable in a rectilinear path between two limiting positions in guides provided on the base, a movable contact element in the form of a rocking arm one end of which has a floating bearing in a housing provided in part by one of the fixed contacts and in part by the other fixed'contact and a torsion spring carried by the plunger for bodily movement therewith having a coiled eye with two arms extending therefrom, the eye fitting over a locating pin in the plunger with one spring arm attached to the other end of the mov able element and the other spring arm engaging a reaction surface on the plunger, the arrangement being such that on initial movement of the plunger from one limiting position towards the other limiting position the element will be rocked about the bearing end aforesaid and the spring will be loaded until a dead-centre position of the element is reached and passed when the movement of the plunger to the other limiting position will be completed by the spring and the bearing end of the element will be moved by a sliding motion under the action of the spring in a direction across the gap so that in one limit- 6 ing position of the plunger the bearing end of the element abuts on both fixed contacts and in the other limiting position it abuts on only one of the fixed contacts.

FRANCIS CECIL FUKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

